Here's what you'll need to do.
If you're behind a firewall, make sure you have the ports you want forwarded. For me, I'm behind a linksys router, so I have the ports for aMule forwarded for TCP and UDP. Once, you have that done then you'll need add aMule into the allowed application in the Mac OS X's firewall, if the firewall is turned on.
Basically, go into 'System Preference, Sharing, Firewall'. Once you click on 'Firewall', on the right hand side you're going to see four radio buttons, 'New, Edit, Delete, and Advanced'. Simply click on 'New'. It will bring up another window.
In this window you'll have 'Port Name, TCP and UDP Port Number(s)'. Click on 'Port Name' and select 'Other' from the list. Now type in the TCP and UDP port number(s) you've selected for aMule, whether you're using the default 4662 and 4672 or something else. Type them in. In the 'Description' you can type in aMule or some other name you choose. Click 'OK' and you're all set to go.
Restart aMule and you should have High ID and Kad will no longer be firewalled.
I hope this helps.
